Investment casting apparatus

ABSTRACT

Investment, or lost wax, casting machine including means for forming an investment mold, melting a metal and pouring it into the mold, condensing steam to produce a partial vacuum, and applying the vacuum to the mold to enhance the flow of metal to the details of the mold.

United States Patent Hudson 1451 Oct. 17, 1972 [54] INVESTMENT CASTING APPARATUS 1,186,558 6/l9l6 Dunn ..l64/255 72 Inventor: Billy 0. Hudson, 1163 El Dorado gg z- '"flfifi Drive, Livermore, Calif. 94550 y [22] Filed: Nov. 19, 1969 Primary Examiner-Robert D. Baldwin 1 pp No: 878,111 Attorney-Flchr, Hohhach, Test, Albntton & Herbert [57] ABSTRACT 52 us. c1. ..164 255, 164/65, 164/335, Investment, lost wax, casting machine including 164/DIG- 4 means for forming an investment mold, melting a In. ..B22d metal and pouring into the mold condensing steam Field of Search 255, 335, 337, to produce a partial vacuum, and applying the vacuum 164/63, 25 D G- 102 to the mold to enhance the flow of metal to the details of the mold. 1 [56] References Cited UNITED STATES PATENTS 6 Claims, 3 Drawing Figures 2,685,718 8/1954 Schmitz .1641255 27 24 28 47 17.26 42 49 2 lo 43 4s 57 1| 469 1i 36 44 5s '51 23 I 77 63 616 62 I BIG 1 e Gld 14 s PATENTEDocI 11 m2 BEST Avmmsm COPY 698'468 lag ATTORNEYS 1 INVESTMENT CASTING APPARATUS BACKGROUND OF THE INVENTION This invention pertains generally to casting processes and more particularly to apparatus for use in investment, or lost-wax, casting.

The basic principles of investment, or lost-wax cast ing were discovered and applied thousands of years ago in China, Egypt, and other parts of the world. The process has been used for hundreds of years for the casting of statues and other artistic works. More recently it has come into use by hobbyists for making small castings, such as jewelry.

SUMMARY AND OBJECTS OF THE INVENTION The casting apparatus of the present invention includes means forforming an investment mold, melting the metal to be cast, and pouring the molten metal into the mold. In addition, it includes means for producing a partial vacuum and applying that vacuum to the mold to enhance the flow of metal into the mold.

It is a general object of the present invention to provide a new and improved casting apparatus which can be utilized in the investment, or lost-wax, process.

Another object of the invention is to provide casting apparatus of the present invention which includes means for melting and pouring the casting material.

Another object of the invention is to provide casting apparatus of the above character which includes means for forming a vacuum and applying the vacuum to the cavity in a mold to enhance the flow of casting material into the cavity.

Additional objects and features of the invention will be apparent from the following description in which the preferred embodiment is set fourth in detail in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT In the preferred embodiment, the casting apparatus comprises generally an investment mold l0, framework means 11 adapted for removably holding the mold, crucible means 12 mounted on the framework means and adapted for holding and pouring molten metal,

resting upon a suitable supporting surface such as'a table top. The platform member 17 is generally parallel to and spaced above the base member 16. The platform member is supported by a plurality of spacer members 19 which extend between the basemember and platform member and are attached thereto by conventional means such as welding or bolting.

A threaded elongate member 21 is mounted on the platform member 17 to provide means for supporting the crucible means 12. The threaded member 21 extends vertically through a mounting hole formed in the platform member 17 and is secured in place by nuts 22 and 23 which engage the upper and lower surfaces of the platform member, respectively. A yoke member 24 is mounted at the upper extremity of the threaded member 21 by means of nuts 26, 26. A shaft 27 is pivotally mounted between the arms of the yoke 24, and a platform 28 is mounted on the shaft 27. In the preferred embodiment, the platform is secured to the shaft by means of rivets. The crucible means 12 is mounted on the platform 28 and is thereby adapted for movement between level and inclined positions. A vertically extending lip 28a is formed at the forward extremity of the platform 28, and a clamp screw 29 is carried by the platform. The lip and clamp screw cooperate to hold the crucible means on the platform.

The crucible means 12 includes a conventional crucible 31 having a well 32 and a spigot 33. The spigot crucible is in its inclined position, the molten metal is discharged through the spigot.

It should be noted that in addition to securing the threaded member 21 to the platform member 17, the nuts 22 and 23 provide means for adjusting the vertical position of the crucible means 12 above the mold 10.

In the preferred embodiment, the heating means 13 includes a source of combustible fluid, such as propane gas. As shown in the drawing, this source is provided by small propane torch of conventional design. This torch includes a tank 36 in which the gas is stored, a valve 37 for metering the flow of gas out of the tank, and a tip 38. The tip 38 is disposed in proximity to the crucible 31, and the tank 36 is mounted on the framework 11 in such a manner that the position of the tip 38 can be adjusted as desired. The tank 36 is clamped to a pair of parallel, spaced apart rod members 41 by means of a resilient spring member 42. The rod members 41 are attached toward their lower extremities to a mounting yoke 43 by conventional means such as welding or riveting. The mounting yoke 43 is pivotally mounted on a shaft 44 carried by another yoke 46 which is attached to the rear portion of the platform member 17. End caps 47, fabricated of a material having a relatively high coefficient of friction are provided at the upper and lower extremities of the rod members 41. The ends of the resilient spring member 42 are attached to the mounting yoke 43, and this spring member urges the tank 36 into engagement with the end caps 47.

Means is provided for adjusting the angle of inclination of the tank 36 relative to the platform member 17. This means includes an eyebolt mounting bracket 48 attached to the platform member 17 and turnbuckle means 49 pivotally connected to the bracket 48 and to the upper portion of one of the rod members 41. The position of the torch can also be adjusted by sliding the tank 36 axially of the rod members 41.

The vacuum means 14 includes a hermetically sealed vacuum chamber 51 formed within a spherical container 52. The container 52 is provided with threaded bushing 53 having a bore 54 communicating with the chamber 51. This bushing extends through an opening in the platform member 17, and a nut 56 is threadedly mounted thereon to secure the container 52 to the platform member. The bore 54 provides means for introducing water into the chamber 51, and a conically tapered plug 57 provides means for closing the bore 54. This plug also serves as a safety valve in the event the pressure within the chamber becomes excessively high.

Means is provided for heating water within the chamber 51. 4 This means includes a conventional source of heat 58 carried by the base member 16 and disposed vertically below the container 52. In the preferred embodiment, the source 58 comprises a container of combustible fuel in jellied form. A plurality of locating studs 59 are attached to the base member 16 to provide means for positioning the fuel supply 58.

A vacuum line 61 is provided for interconnecting the vacuum chamber 51 with the mold to provide communication between the chamber and the mold cavity. This line includes a first section 61a communicating .with the chamber 51 and connected at one end to a fitting 62 mounted on the container 52. The other end of the section 610 is connected to the inlet side of a valve 63. A second section 61b of the vacuum line extends between the discharge side of the valve and a T fitting 64. The vacuum line 61 also includes an upper section 610 which extends from the upper side of the T- fitting 64 through an opening 66 in the platform 17. The upper end of the section 61c extends above the platform member and into a connector 67. The connector 67 is formed to include a passageway 68 to provide communication between the line 61 and the mold cavity. The outer contour of the connector includes a cylindrical lower section 69, a cylindrical upper section 71 of smaller diameter than the lower section, and a conically tapered shoulder 72 intermediate the upper and lower sections. In the preferred embodiment, the connector 67 is fabricated of metal and is attached to the line 61 by threads.

The vacuum line 61 is formed to include trap means for preventing foreign matter, such as molten metal and particles of the mold, from being drawn into the vacuum chamber 51. This trap means includes a trap section 61d connected to the lower side of the T-fitting 64 and located below and in axial alignment with the passageway 68 in the connector 67. The cap 73 is removably attached to the lower end of the trap section to permit cleaning of this section.

4 The valve 63 provides means for controlling the communication between the vacuum chamber 51 and the mold cavity. In the preferred embodiment, this valve comprises a conventional stopcock having a butterfly member adapted for movement between open and closed positions through rotational movement on the order of Linkage means is provided for interconnecting the crucible means 12 and the valve 63 in such manner that the position of the crucible corresponds to the position of the butterfly member in the valve. This means in cludes a shaft 76 operably connected at one end to the butterfly member of the valve and pivotally supported toward its other end by a bracket 77 attached to the under surface of the platform member 17. An operating handle 78 is connected near the outer extremity of the shaft 76 to provide means for rotating the shaft. The linkage means also includes a crank 81 attached to the shaft 76 proximate to the handle 78, an elongate member 82 having its upper end pivotally connected to the rear portion of the crucible platform 28, and an adjustable clamp member 83 pivotally connecting the lower portion of the elongate member 82 to the crank 81. The clamp member 83 can be adjusted axially of the elongate member 82 to provide means for adjusting the length of the linkage and the relative positions of the crucible andvalve. In FIG. 1, the valve 63 is shown in its closed position, and the crucible is level. When the valve is opened by rotating the operating handle 78 in a clockwise direction, the crucible is moved to its inclined position.

The investment mold 10 is adapted to be removably mounted on the upper surface of the platform member 17, with the connector 67 extending into the lower portion of the mold. The mold includes a cylindrical sleeve or flask 86 which preferably has a substantially flat surface 86a at one end to provide a good sealing surface. A rubber gasket 87 is disposed between the surface 86a and the upper surface of the platform member 17 to insure a good seal during investment. This sleeve is adapted for holding a conventional investment material 88 which is formed to define a mold cavity 89, a funnelshaped sprue 91, and a gate 92 interconnecting the sprue and cavity. In addition, the investment material 88 is formed to define air passageways 93 which communicate with the cavity 89 through the porous investment material and which are adapted for communicating directly with the passageway 68 in the connector 67. Suitable investment materials include refractory material such as silica in the form of quartz of cristobalite, with a gypsum plaster binder.

Operation and use of the casting apparatus in a lostwax process can now be described briefly as follows: Let it be assumed that the rubber gasket 87 has been placed over the connector 67 and is resting upon the upper surface of the platform member 17. Further let it be assumed that a wax pattern has been prepared in the conventional manner and that a wax column has been attached to the pattern to provide means for forming the gate 92. A cradle for the pattern is formed by bending columns of wax, commonly known as wax wires, into a form generally corresponding to the contour of the pattern. The cradle is attached to the upper portion of the connector 67 by additional wax, and this cradle provides means for forming the air passageway 93.

Preferably, the cradle and wax attaching it to the con-' nector should seal the passageway 68 to prevent investment material from entering this passageway during formation of the mold.

A coating of investment material is formed on the pattern, and the coated pattern is placed in the cradle, with the wax column for forming the gate extending in an upward direction. The coating can be conveniently formed by brushing successive layers of investment material in slurry form onto the pattern. It is important that the coating have a sufficient thickness to prevent cave-ins between the cavity and the air passageways. A thickness on the order of one-eighth inch has been found to give satisfactory results in casting pieces of jewelry, such as rings.

After the pattern has been placed in the cradle, the

' sleeve 86 is placed over the pattern, with its lower surface 86a resting on the rubber washer 88. A slurry of investment material is poured into the sleeve and allowed to harden.

After the investment material has hardened, the mold and rubber gasket are removed from the platform member 17, and the funnel-shaped sprue 91 is formed by cutting away a portion of the investment material.

The wax is removed from the hardened mold by conr ventional means, such as heating in an oven or furnace to a temperature on the order of l,O to 1,200 F. Alternatively, the wax can be removed by means of a solvent-vapor bath, such as trichloroethylene vapor. After the wax has been removed, the mold is maintained at a temperature on the order of 700 to l,000 F, the exact temperature depending upon the metal to be cast. Maintaining the mold at this temperature tends to vaporize and eliminate any wax which remains in the mold, and it facilitates the flow of metal in the mold during the casting process.

While the mold is being heated, a vacuum is formed in the vacuum chamber 51. For this purpose, the plug 57 is removed and water is introduced into the chamber through the opening 54. The water is then heated by means of heat source 58 until it vaporizes and there is a steady flow of steam from the opening 54. The heat source is then extinguished, the plug 57 is replaced, and the chamber is allowed to cool. When chamber cools to room temperature, the steam will condense, producing a pressure on the order of one two-hundreds of an atmosphere in the chamber.

After the vacuum has been formed, the metal to be cast is placed in the crucible 31 and melted by means of the torch 13. When the metal is ready for casting, the heated mold is replaced on the platform member 17, with the connector 67 engaging the investment material in a sealing relationship. The valve 63 is opened by rotating the handle 78 which causes the crucible means 12 to move to its inclined position, pouring the metal into the sprue 91. The molten metal flows downwardly through the gate 92 and into the cavity 89. The difference in pressure between the vacuum chamber 51 and the sprue 91 which is exposed to the atmosphere enhances the flow of metal into the details of the cavity. When the casting has cooled, it can be removed from the mold and finished in a conventional manner.

It is apparent from the foregoing that a new and improved casting apparatus has been provided. This apparatus combines means for performing substantially all of the steps of the investment, or lost-wax, process ing a generally planar surface for supporting the mold in an upright position, a mandrel member having a passageway mounted on said generally planar surface, said mandrel member extending above said planar surface a substantial distance into the investment material in the lower portion of said mold when said moldis placed on said surface, one end of the passageway is said mandrel member being in closeproximity to the mold cavity, a vacuum line for connecting the passageway in said mandrel member to a vacuum source, valve means movable between open and closed positions connected to said vacuum line forcontrolling communication between said vacuum source and said passageway, a crucible mounted on said framework above said generally planar surface, said crucible being movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold and means linking said crucible and said valve means together in such manner that said crucible is constrained for movement with said valve means.

2. Casting apparatus as in claim 1 together with heat ing means mounted on said framework means for heat-.

ing the metal in said crucible.

3. Casting apparatus as in Claim 1 wherein said vacuum line is formed to include trap means for preventing foreign matter from being drawn into the mold.

4. In casting apparatus, a framework having a generally planar surface, a mold formed of investment material supported by said planar surface, said mold including a mold cavity defined by the investment material, a mandrel member mounted on said planar surface extending into the lower portion of said mold and forming a vacuum seal therewith, said mandrel member including a passageway communicating with the mold cavity through the investment material, vacuum forming means mounted on said framework forming an integral part of said apparatus, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, a vacuum line connecting said chamber to the passageway in said mandrel member, valve means movable between open and closed positions for controlling the communication between said chamber and said passageway, a crucible mounted on said framework above said mold movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold, linkage means connecting said crucible and said valve means in such manner that said crucible is constrained for movement with said valve means, a gas burning torch, a source of gas for said'torch, and means mounted on said framework for holding said torch and source and positioning the same relative to said crucible.

5. A self-contained portable casting machine particularly suitable for use in making a lost wax casting in an investment mold, said machine comprising a framework having a generally planar surface for supporting the mold in an upright position, vacuum forming means carried by said framework forming an integral part of said machine, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, means including a valve movable between open and closed positions for connecting said chamber in communication with the interior portion of the mold on said planar surface, a crucible mounted 'on said framework above said planar surface movable between a first portion for retaining molten metal and A second position for pouring molten metal into said mold, linkage interconnecting said crucible and said valve in such manner that said crucible is constrained for movementin an upright position, a mandrel member having a passageway mounted on said generally planar surface, said mandrel member extending above said planar surface a substantial distance into the investment material in the lower portion of said mold when said mold is placed on said surface, one end of the passageway in said mandrel member being in close proximity to the mold cavity, vacuum forming means carried by said framework means, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, a vacuum line connecting said chamberlin communication with the passageway in said mandrel member, a crucible mounted on said framework above said generally planar surface, said crucible being movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold, and heating means carried by said framework for heating the metal in said crucible. 

1. In apparatus for making a casting in an investment mold, said mold comprising a mold cavity formed in a body of investment material, framework means including a generally planar surface for supporting the mold in an upright position, a mandrel member having a passageway mounted on said generally planar surface, said mandrel member extending above said planar surface a substantial distance into the investment material in the lower portion of said mold when said mold is placed on said surface, one end of the passageway in said mandrel member being in close proximity to the mold cavity, a vacuum line for connecting the passageway in said mandrel member to a vacuum source, valve means movable between open and closed positions connected to said vacuum line for controlling communication between said vacuum source and said passageway, a crucible mounted on said framework above said generally planar surface, said crucible being movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold and means linking said crucible and said valve means together in such manner that said crucible is constrained for movement with said valve means.
 2. Casting apparatus as in claim 1 together with heating means mounted on said framework means for heating the metal in said crucible.
 3. Casting apparatus as in Claim 1 wherein said vacuum line is formed to include trap means for preventing foreign matter from being drawn into the mold.
 4. In casting apparatus, a framework having a generally planar surface, a mold formed of investment material supported by said planar surface, said mold including a mold cavity defined by the investment material, a mandrel member mounted on said planar surface extending into the lower portion of said mold and forming a vacuum seal therewith, said mandrel member including a passageway communicating with the mold cavity through the investment material, vacuum forming means mounted on said framework forming an integral part of said apparatus, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, a vacuum line connecting said chamber to the passageway in said mandrel member, valve means movable between open and closed positions for controlling the communication between said chamber and said passageway, a crucible mounted on said framework above said mold movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold, linkage meaNs connecting said crucible and said valve means in such manner that said crucible is constrained for movement with said valve means, a gas burning torch, a source of gas for said torch, and means mounted on said framework for holding said torch and source and positioning the same relative to said crucible.
 5. A self-contained portable casting machine particularly suitable for use in making a lost wax casting in an investment mold, said machine comprising a framework having a generally planar surface for supporting the mold in an upright position, vacuum forming means carried by said framework forming an integral part of said machine, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, means including a valve movable between open and closed positions for connecting said chamber in communication with the interior portion of the mold on said planar surface, a crucible mounted on said framework above said planar surface movable between a first portion for retaining molten metal and A second position for pouring molten metal into said mold, linkage interconnecting said crucible and said valve in such manner that said crucible is constrained for movement with said valve, and heating means forming an integral part of said apparatus for heating the metal in said crucible.
 6. In apparatus for making a casting in an investment mold, said mold comprising a mold cavity formed in a body of investment material, framework means including a generally planar surface for supporting the mold in an upright position, a mandrel member having a passageway mounted on said generally planar surface, said mandrel member extending above said planar surface a substantial distance into the investment material in the lower portion of said mold when said mold is placed on said surface, one end of the passageway in said mandrel member being in close proximity to the mold cavity, vacuum forming means carried by said framework means, said vacuum forming means including heating means and means defining a chamber for boiling water and condensing steam, a vacuum line connecting said chamber in communication with the passageway in said mandrel member, a crucible mounted on said framework above said generally planar surface, said crucible being movable between a first position for retaining molten metal and a second position for pouring molten metal into said mold, and heating means carried by said framework for heating the metal in said crucible. 